1. Field of the Invention
The present invention relates in general to canisters for the storage of fluid or semi-fluid materials. In particular, the present invention relates to an improved canister for such materials which includes an integral plunger which may be moved through the container body to extrude the fluid or semi-fluid material from the container.
2. Description of the Related Art
It has been known to provide containers for material having a low viscosity, such as semi-solid or semi-frozen liquid food stuffs which provide a dispensing feature. This is particularly prevalent in the field of sauces and other materials for use in fast food outlets. Such containers typically include an elongated container body having a dispenser opening or spout at a first end and a movable sealing plunger at the second end. The container is placed within an appropriate device for holding the container and the plunger is moved towards the first end containing the spout. This movement of the plunger forces the material within the container through the spout for dispensing. Examples of such containers are shown in U.S. Pat. Nos. 2,927,543 to Sherbondy, 3,884,396 to Gordon, et al., 4,326,650 to Van Manen, and 4,356,935 to Kamin.
One of the concerns with such containers is container integrity, especially at the rear, plunger end of the container. In the prior art devices a poor seal about the periphery of the plunger will allow moisture and air to pass into the container, causing contamination or spoilage of the material to be dispensed. Additionally, an poor plunger seal will allow the material to pass between the plunger and the container side wall, reducing the amount of material which may be dispensed and creating a cleanup and spoilage problem.
One arrangement to provide a better plunger seal is shown in U.S. Pat. No. 4,027,810 to Van Manen. This reference shows a plunger having a soft resilient material surrounding a rigid core. The soft material conforms to the interior of the container to provide an effective seal. While the sealing characteristics of this plunger are adequate, the two-part construction raises the cost of the container.
Additional factors which raise the cost of such dispensing containers, and make them less attractive, are the junctions between the plunger and the container in the initial position of the plunger, the junction between the container side wall and the lid of the container and the initial seal across the dispensing spout. To provide adequate seals against contamination and leakage, these junctions and seals are typically of a complicated nature requiring several assembly steps. This of course increases the cost of such containers.